The aim of this study was to examine the relation of parental supervision, parental involvement at school and child's social competence with school achievement in primary school. A theoretical model was postulated that predicts direct and indirect effects of parental behaviors on adolescents' school achievement. Participants were 1,024 adolescents attending Grades 5 through 8 in 20 primary schools in Croatia and one of their parents or guardians. Adolescents completed a scale assessing their self-perceived social competence and data on their grade point average were collected. Parents completed scales measuring parental supervision and parental involvement at school and they rated their child's social competence. The results of model testing showed that parental behaviors have both direct and indirect effect on adolescents' school achievement. Greater parental supervision and school involvement have a direct and an indirect, through their effects on child's social competence, positive effects on adolescents' school achievement.